GONADOLIBERIN DERIVATIVES AND PROCESS FOR PREPARING THEREOF

The invention relates to gonadoliberin derivatives of the general formula (I) Glp-His-Trp-Ser-Tyr-X1-X2-X3-Pro-X4 wherein X1 is a glycyl group or a D-isomer of any natural or synthetic amino acid group, X2 represents an L-amino acid group having 1 to 4 carbon atoms in the side chain, L-phenyl-alanyl or L-tryptophyl group, X3 represents an L-amino acid group having a C1-4 alkyl or C2-4 alkanoyl-amide side chain, and X4 is a glycine amide or a C1-4 alkyl amide group, with the proviso that if X1 stands for a group other than glycyl and X2 is a tryptophyl group then X3 may not be leucyl, and the addition salts formed with therapeutically useable acids and complexes thereof. Furthermore the invention relates to a process for preparing these compounds. The new gonadoliberin derivatives can be effectively used for the reproduction process of fish, birds and mammals.